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Abstract:

Provided are methods and components related to preventing hydrocarbon
residue buildup in engine components. Prevention is achieved using a
coating of a mixed metal oxide. The mixed metal oxide comprises a mixture
of at least two of Gd, Al, Ti, Ce, Pr, La, Y, Nd, and Mn. The coating can
also contain amounts of precious metals, eg. Pt, Pd, Rh and/or Au.

5. The article component of claim 1, wherein the coating is catalytically
active.

6. The article of claim 4, wherein the coating comprises Pd in the range
of 1% to 5% by weight and ceria in the range of 5% to 60% by weight on a
oxide basis, and oxides of rare earth metals in the range of 5-20% by
weight on an oxide basis.

7. The article of claim 1, wherein the coating further comprises
lanthanum oxide and zirconia in an amount of about 50% by weight on an
oxide basis.

Description:

[0001] This application claims priority under 35 U.S.C. §119(e) to
Provisional U.S. Patent Application No. 61/472,318, filed Apr. 6, 2011,
which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The invention relates generally to the field of combustion engines,
and specifically to coatings for preventing hydrocarbon residue buildup
on engine and/or powertrain components.

BACKGROUND

[0003] Internal combustion piston engines with carburetion or fuel
injection are very well known. These engines usually have several
cylinders, where an axially-moving piston encloses a combustion chamber.
In these combustion chambers, combustion of a fuel-air mixture fed into
the combustion chamber occurs.

[0004] A pervasive problem of these internal combustion engines is the
formation of carbonization residues from unburnt fuel and lubrication oil
fed to the engine. These residues are bituminous and, in part, highly
complex mixtures of hydrocarbons. The residues are deposited and
accumulate on various engine and powertrain structural components. This
includes valves, piston surfaces, intake ports, injection nozzles, and
the upper surface of the combustion chamber. These carbonization residues
may accumulate to such an extent, especially on intake valves, that they
produce undesired changes in the fluid dynamics or closing behavior of
the valve. Carbonization residues can also have very negative effects on
other component surfaces of the combustion chamber (e.g., the piston
working surfaces). Another frequently encountered problem is deposit
build up on turbochargers, mainly the compressor housing. This is
particularly problematic for engines with positive crankcase ventilation.
Thus, there is a need for methods and compositions for preventing such
buildup.

[0006] Accordingly, one aspect of the invention relates to an article
comprising an engine or powertrain component and a coating applied to the
engine or powertrain component, the coating comprising a mixed metal
oxide, the mixed metal oxide comprising Ce, Pr, Al, Zr and La. In one
embodiment, the engine or powertrain component is selected from the group
consisting of turbocharger, valve, piston, piston fireland, firedeck,
compressor housing, intake port, injection nozzle, combustion chamber,
shroud, swirl generator and combinations thereof.

[0007] In another embodiment of this aspect, the coating further comprises
a precious metal. In a further embodiment, the precious metal comprises
Pd. In yet another embodiment, the coating is catalytically active. In a
specific embodiment, the coating comprises Pd in the range of 1% to 5% by
weight and ceria in the range of 5% to 60% by weight on a oxide basis,
and oxides of rare earth metals in the range of 5-20% by weight on an
oxide basis. In another variant, the coating further comprises lanthanum
oxide and zirconia in an amount of about 50% by weight on an oxide basis.
In a very specific embodiment, the coating comprises about 3 wt % Pd,
about 30% ceria, about 7 wt % oxides of Pr and La, about 40 wt %
zirconia, and about 20 wt % alumina.

[0008] Another aspect of the invention relates to a method of preventing
hydrocarbon deposit buildup on engine or powertrain components, the
method comprising applying a coating on an engine or powertrain
component, the coating comprising a mixed metal oxide, the mixed metal
oxide comprising at least two metals selected from the group consisting
of Gd, Al, Ti, Ce, Pr, La, Y, Nd, Mn, Zr and combinations thereof. In one
embodiment, the engine or powertrain component is selected from the group
consisting of turbocharger, valve, piston, piston fireland, firedeck,
compressor housing, intake port, injection nozzle, combustion chamber and
combinations thereof. In one or more embodiments, the coating is applied
by dip coating, thermal spraying, plasma spraying, airbrushing,
impregnation, atomic layer deposition or combinations thereof.

[0009] In another embodiment, the coating further comprises a precious
metal. In other variants, a Ni/Al bond-coat is used. In yet other
variants, the coating is applied to a metallic surface of the engine or
powertrain component.

[0010] In other embodiments still, the coating is catalytically active to
prevent carbonization residue, or the coating is modified by
post-deposition or post-impregnation thereby providing the precious metal
on the surface of the coating. In a very specific embodiment, the coating
comprises about 3 wt % Pd, about 30% ceria, about 7 wt % oxides of Pr and
La, about 40 wt % zirconia, and about 20 wt % alumina.

[0013] FIG. 3 is a graph showing combustion product CO obtained on samples
coated in accordance with one or more embodiments of the invention and a
comparative sample; and

[0014]FIG. 4 is a graph showing combustion product CO2 obtained on
samples coated in accordance with one or more embodiments of the
invention and a comparative sample.

DETAILED DESCRIPTION

[0015] Before describing several exemplary embodiments of the invention,
it is to be understood that the invention is not limited to the details
of construction or process steps set forth in the following description.
The invention is capable of other embodiments and of being practiced or
being carried out in various ways.

[0016] Residue buildup occurs as a result from unburned hydrocarbons,
lubricant oil and soot. The problem of residue buildup can occur on the
surfaces of various engine and/or powertrain components, including, but
not limited to the turbocharger, valve, piston, piston fireland,
firedeck, compressor housing, intake port, injection nozzle, shroud,
swirl generator and combustion chamber. In one or more embodiments, the
component has grooves or indentations on the surface of the component.

[0017] Accordingly, one aspect of the invention relates to a coating that
prevents deposit buildup on engine and powertrain components. One
embodiment of the invention pertains to an article component comprising
an engine or powertrain component and a coating applied to the engine or
powertrain component. Without a coating, the engine or powertrain
component would have at least some of its surface exposed to
hydrocarbons. In one embodiment, the coating is applied to a component
that is on the intake side of a turbocharger, as opposed to the exhaust
side.

[0018] One or more embodiments of the invention provide a coating that
prevent deposit buildup from occurring. That is, the residue that
normally accumulates on the surface of various engine and/or powertrain
components never has the opportunity to collect on these surfaces. While
not wishing to be bound to a particular theory, it is thought that the
coating helps combust the residues at low temperatures. It is thought
that the coating does not work as a simple repellant.

[0019] The coating comprises a mixed metal oxide, which is comprised of at
least two metals selected from the group consisting of Al, Ti, Gd, Ce,
Pr, La, Y, Nd, Zr and Mn. In another embodiment, the coating also
comprises a precious metal, for example, Pt, Pd, Rh and/or Au. In one or
more embodiments, the coating is catalytically active to remove
hydrocarbon deposits on engine components. In a specific embodiment, the
coating comprises Pd and another component selected from those provided
above. In a further embodiment, the coating comprises Pd in the range of
1% to 5% by weight and ceria in the range of 5% to 60% by weight on a
oxide basis, and oxides of rare earth metals in the range of 5-20% by
weight on an oxide basis.

[0020] In another embodiment, the coating comprises a mixed metal oxide,
the mixed metal oxide comprising Ce, Pr, Al and La. In a further
embodiment, the coating comprises about 3 wt % Pd, about 30% ceria, about
7 wt % oxides of Pr and La, about 40 wt % zirconia, and about 20 wt %
alumina.

[0021] According to one or more embodiments, the metal oxides are in
particulate form. In specific embodiments, particles of high surface
area, e.g., from about 100 to 500 square meters per gram ("m2 /g")
surface area, specifically from about 150 to 450 m2/g, more
specifically from about 200 to 400 m2/g, are desired so as to better
disperse the catalytic metal component or components thereon. The first
layer refractory metal oxide also desirably is mesoporous and has a high
porosity of pores up to 1456 Angstroms radius, e.g., from about 0.75 to
1.5 cubic centimeters per gram ("cc/g"), specifically from about 0.9 to
1.2 cc/g, and a pore size range of at least about 50% of the porosity
being provided by pores of 50 to 1000 Angstroms in radius. For alumina
particles, it may be desirable to utilize a high surface area mesoporous
gamma alumina, for example GA-200.

[0022] Another aspect of the invention relates to a method of preventing
residue buildup. One embodiment pertains to a method of preventing
hydrocarbon deposit buildup on engine or powertrain components, the
method comprising applying a coating on an engine or powertrain
component, the coating comprising a mixed metal oxide, the mixed metal
oxide comprising at least two metals selected from the group consisting
of Al, Ti, Ce, Pr, La, Y, Nd, Mn, Zr and combinations thereof. In a
further embodiment, the applied coating further comprises a precious
metal.

[0023] The coating may be applied to any deposit-prone engine or
powertrain component including, but not limited to, the turbocharger,
valve, piston, piston fireland, compressor housing, intake port,
injection nozzle and combustion chamber. In a specific embodiment, the
coating is applied to a metallic surface of the engine or powertrain
component.

[0024] The coatings described herein may be applied using a variety of
methods. Various methods of application include, but are not limited to,
dip coating, thermal spraying, plasma spraying, airbrushing,
impregnation, and atomic layer deposition. In one embodiment, the coating
is applied via suspension plasma spraying. In another embodiment, a Ni/Al
bond-coat may be used to enhance thermal stability of coating. In another
embodiment, a post-deposition or post-impregnation process may be used to
enhance the coating. In order to reduce the overall precious metal
content of the coating, post-impregnation can be used such that the
precious metal would be present at the surface only. The other ceramic
layer would only provide the surface adhesion to the metal, like a bond
coat. Generally speaking, a slurry which meets the proper solids %
content and rheology can be loaded into an apparatus which utilizes
pressurized air to generate a spray pattern consisting of fine droplets.
This apparatus could be one of a few different units, including, but not
limited to: paint spray guns, glass mist sprayers, and pressurized spray
bottles. The apparatus used can have various settings adjusted to control
the droplet size, spray pattern/shape, and amount of slurry sprayed per
unit of time. The method could involve multiple passes with the spray
gun, and could involve drying and/or calcining between coatings.
Different layers can also be applied in this fashion. Another method that
can be employed is dipping the substrate into a slurry, then using an air
knife to blow off excess slurry until a desired coating is attained.

[0025] In one embodiment, the coating is applied using a suspension plasma
technique. This technique comprises suspending a mixed metal oxide in a
suspension; atomizing the slurry with suspended mixed metal oxide into a
suspension plasma as described further below; and spraying the suspension
plasma onto a engine, exhaust-gas-system or powertrain component.
Optionally, the suspension plasma may be sprayed only onto the surface of
the engine, exhaust-gas-system or powertrain component that is prone to
residue buildup.

[0026] Exemplary suspension plasma spray methods according to one or more
embodiments involve several process steps. First, solid particles are
dispersed into a liquid and kept in suspension during the process.
Second, the suspension is fed and injected into a heat source. Next, the
solid particles in suspension are at least partially melted and impact on
a surface of an article to form a deposit. The heat source in plasma
spraying can include, but is not limited to electric arc plasma, RF
plasma or microwave plasma. Suitable examples of suspension plasma
spraying are described in U.S. Pat. Nos. 5,609,921, 6,277,448, and
4,376,010, the entire content of each patent being incorporated herein by
reference.

[0027] Suspension plasma spraying, according to one or more embodiments,
involves a plasma spray deposition method for producing a material
deposit onto a substrate. The method can comprise producing a plasma
discharge; providing a suspension of a material to be deposited, this
suspension comprising small solid particles of that material dispersed
into a liquid or semi-liquid carrier substance; atomizing the suspension
into a stream of fine droplets and injecting the stream of fine droplets
within the plasma discharge; and by means of the plasma discharge, (a)
vaporizing the carrier substance, (b) agglomerating the small particles
into at least partially melted drops, (c) accelerating these drops, and
(d) projecting the accelerated drops onto the substrate to form the
material deposit.

[0028] The probe atomizes the suspension into a stream of fine droplets
and injects this stream of droplets generally centrally of the plasma
discharge. The suspension is then sheared and thereby atomized, and
injected in the plasma discharge under the form of fine droplets through
the opening. Although an example of suspension plasma spraying process
and apparatus have been described hereinabove, the present invention is
not limited to the process as apparatus described, and alternative
atomizing processes are available to shear the suspension.

[0029] The stream of fine droplets travels through the plasma discharge to
reach the substrate. As the droplets of suspension travel from the
opening to the substrate, these droplets are subjected to several
physicochemical transformations. The suspension is typically composed of
small solid particles suspended and dispersed into a solvent or other
liquid or semi-liquid carrier substance. When the fine droplets of
suspension reach the plasma discharge, the solvent first evaporates and
the vapor thus formed decomposes under the extreme heat of the plasma.
The remaining aerosol of small solid particles then agglomerate into
drops which are either totally or partially melted and/or vaporized. The
plasma discharge accelerates the molten drops, which accumulate kinetic
energy. Carried by this kinetic energy, the drops hit the substrate. The
plurality of drops form on the substrate a layer of partially or totally
melted drops partially overlapping one another.

COMPARATIVE EXAMPLE 1

[0030] A coating of pure aluminum was prepared on a test planchette. The
test planchette consists of pure aluminum, and is free of any coating. It
thus serves as a comparative example, and is representative of, for
example, a turbocharger aluminum surface.

EXAMPLE 2

[0031] A coating was deposited on a planchette via air spray. A slurry
which met the proper solids % content and rheology was loaded into an
apparatus which utilizes pressurized air to generate a spray pattern
consisting of fine droplets. The coating included a mixed oxide of Ce,
Zr, La, and Gd oxides. The composition was as follows: 31% Ce, 45%Zr, 10%
Y, 14% (La+Gd).

Testing of Examples

[0032] On the planchette, soot and oil were applied to the surface, and a
temperature ramp was applied in air. Combustion product CO and CO2
development were measured. Planchettes with soot/oil mixture on the
surface of the planchettes were placed in a furnace. The furnace was ramp
in temperature at 15 K/min. The gas temperature right above the
planchettes was measured by means of an additional type K thermocouple.
The gases above the planchettes are extracted with a nozzle. This gas was
analyzed for CO and CO2 using an Uras 14, Advance Optima module from
ABB which uses infrared light. From this measurement, the catalytic
activity of the coating for hydrocarbon oxidation was deduced. In FIG. 1
the CO signal is displayed, and in FIG. 2 the CO2 signal is shown.
In FIG. 1, which shows the CO signal, there are three peaks developing
over temperature for the aluminum planchette are present. The first peak
reflects lube oil burning, the third peak reflects soot burning, but the
second peak, however, around 400° C. reflects the burning of oil
residues. No such second peak is apparent for a catalytic surface made
from mixed Ce, Zr, La, Gd oxide Thus, no oil residue deposits are formed
in this case. The explanation can be seen in FIG. 2. A strong CO2
signal is apparent for the catalyst-coated surface. This reflects the
complete combustion of the oil components. On the contrary, no CO2
signal is shown on the uncoated aluminum surface. The oil is combusted
incompletely, and residues of partially burned or cracked hydrocarbons
remain on the pure aluminum surface.

[0037] Comparative Example 7. A coating of 100% zirconia was deposited on
a planchette. This example is considered to be a reference sample for
inactive coatings because Zr is generally inactive.

Testing of Examples 3-7

[0038] Testing was conducted similarly as above, and results are shown in
FIGS. 3 and 4. The inclusion of Pd shows very promising results. Examples
3 and 4, the Pd-containing samples, have the lowest oil burning peak
temperatures and show the highest oxidation activity. In the CO signal,
it can be seen that the oxidation reaction starts below 250° C.
and in the CO2 signal, it can be seen that oxidation peaks at around
300° C. for the Pd-containing samples. While the absolute
temperatures of this test cannot be necessarily compared to real world
applications, the tests above show temperature shift in lowering the
burning temperature for hydrocarbon deposited on the planchettes. Carbon
buildup is prevented by burning off hydrocarbon. In engine applications,
for instance, the oil loading will be much lower in the final
application. However, the results are very valuable to compare the
relative performance of the samples for oil oxidation and hence their
ability to prevent deposit formation. Zirconia is widely inactive as can
be seen in the low CO2-signal intensity.

[0039] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment" means
that a particular feature, structure, material, or characteristic
described in connection with the embodiment is included in at least one
embodiment of the invention. Thus, the appearances of the phrases such as
"in one or more embodiments," "in certain embodiments," "in one
embodiment" or "in an embodiment" in various places throughout this
specification are not necessarily referring to the same embodiment of the
invention. Furthermore, the particular features, structures, materials,
or characteristics may be combined in any suitable manner in one or more
embodiments.

[0040] Although the invention herein has been described with reference to
particular embodiments, it is to be understood that these embodiments are
merely illustrative of the principles and applications of the present
invention. It will be apparent to those skilled in the art that various
modifications and variations can be made to the method and apparatus of
the present invention without departing from the spirit and scope of the
invention. Thus, it is intended that the present invention include
modifications and variations that are within the scope of the appended
claims and their equivalents.